Vibration is a serious problem in helicopters. The action of the rotor blades and the air loading on the blades generate vibration forces which are oriented both vertically and in the plane of the rotor disc. Both types of vibrations are transmitted through the rotor pylon to the helicopter transmission where the vibrations are passed on to the helicopter fuselage. Vibration of the fuselage has been reduced by use of nodal point isolators. A number of nodal point isolation systems have been developed to reduce such vibration. These vibration suppression devices are disclosed in U.S. Pat. No. 3,845,917 to Drees, U.S. Pat. No. 3,857,534 to Drees et. al. and U.S. Pat. Nos. 3,858,831 and 3,945,628 to Halwes. The devices disclosed in these patents however, provide isolation for no more than three degrees of freedom.
There exists a need for a vibration suppression system which provides isolation for as many as five degrees of freedom to reduce inplane as well as vertical vibrations which are generated in the rotor pylon and transmitted to the fuselage through the transmission.